Angiographic Evaluation of the Graft Patency

Coronary angiography was performed three months after the operation with the patient’s consent, regardless of any symptoms of angina pectoris. Coronary computed tomography angiography (CTA) was chosen because of its minimally invasive nature and reliability in identifying graft occlusion.⁷ Patients who had died, who refused angiographic evaluation, who were unable to complete coronary CTA, or who had impaired renal function were excluded from the angiographic follow-up. Coronary CTA was performed with a 128-slice spiral CT machine (Philips Brilliance ICT, Cleveland, USA). The heart rate of all subjects was controlled at 75 beats/min. Breath hold training and heart rate measurement were carried out one hour before the examination. If the heart rate was >75 beats/min and the patient had no contraindications, the patient had to take 10 mg of metoprolol orally. The whole heart was scanned, the data were processed for surface reconstruction and spherical display, and the results were recorded and analyzed. In all subjects, coronary CTA was performed by manual injection of 1 mg/kg iodixanol. All the images were assessed through visual evaluation by two imaging experts from our center. No stenosis indicated fully unobstructed, stenosis <50% was mild stenosis, stenosis of 50–75% was moderate stenosis, and stenosis >75% was considered to be severe.